5 1. Field of the Invention
This invention relates to a polyester film excellent in antistatic property, adhesion property and also transparency, and a light-sensitive silver halide photographic material using said polyester film.
2. Prior Art
A polyester film, particularly a polyethylene terephthalate biaxially oriented film has been used as a base for a photographic film, a base for drawing and a base for a magnetic recording tape. In these uses, a subbing layer is generally provided between a polyester support and a surface layer material to improve adhesion property therebetween. As such a subbing layer, in Japanese Patent Publication No. 40873/1972, there is disclosed a copolymer containing 8 mole % or more of a compound having a metal salt group of an ester-forming sulfonic acid based on the whole acid component and 20 mole % or more of polyethylene glycol based on the whole glycol component for the purpose of water dispersion. However, it can be easily estimated that water resistance of adhesion is lowered. In Japanese Patent Publication No. 5476/1981, a saturated linear aliphatic dicarboxylic acid having 4 to 8 methylene groups is used. However, also in this case, water resistance of the subbing layer is not sufficient. In Japanese Provisional Patent Publication No. 88454/1981, a substantially water-insoluble aqueous dispersion is used for improving water resistance. However, since the dispersion contains a water-soluble organic solvent, problems of working environment remain unsolved. In Japanese Provisional Patent Publication No. 248231/1985, there is disclosed a polyester aqueous dispersion in which a polyester having an intrinsic viscosity of 0.2 to 0.8 and substantially insoluble in water is uniformly dispersed in water containing no organic solvent. The above polyester comprises at least 40 mole % of terephthalic acid and 0.5 to 5 mole % of an aromatic dicarboxylic acid containing a metal salt of a sulfonic acid as acid components, and 5 to 60 mole % of ethylene glycol and neopentyl glycol as glycol components. In working examples thereof, the polymer insoluble in water is dissolved in tetrahydrofuran and then dispersed in water to obtain an aqueous dispersion, and then the solvent is removed by evaporation under reduced pressure, and there is also described clearly that the polymer is dissolved in a hydrophilic organic solvent such as acetone, tetrahydrofuran, ethyl acetate and methyl ethyl ketone to obtain an aqueous dispersion. Since an organic solvent is used in the process of preparing a water dispersion, problems of working environment are caused and also the steps of preparing the aqueous dispersion become complicated, whereby the above technique is not preferred in practical use.
Further, in such prior techniques, it is difficult to impart excellent transparency and antistatic property at the same time to a subbing layer. In Japanese Provisional Patent Publication No. 164831/1986, there is disclosed a technique of providing a subbing layer which is transparent, has antistatic property and also satisfies adhesion property. However, adhesion property to a hydrophilic colloid layer is poor, and a water-soluble organic solvent is contained so that there involve various problems such as problems of working environment and problems of preventing explosion of a stretching instrument and taking measures to prevent environmental pollution.
Under such a situation, in Japanese Provisional Patent Publications No. 20424/1986, No. 9242/1989 and No. 272535/1990, there have been proposed techniques of laminating a composition obtained by mixing an acrylic polymer or a polyester copolymer and a polymer having conductivity on a plastic film support. However, since compatibility of the acrylic polymer or the polyester copolymer with the conductive polymer is insufficient, there is a problem that whitening phenomenon occurs in the film obtained.